1. Field of the Invention
The present invention relates to a throttle grip apparatus which not only can control an engine of a vehicle in accordance with the detected value of a throttle opening angle sensor but also includes an energizing unit for returning a throttle grip after rotated to its initial state.
2. Description of the Related Art
In a recent two-wheeled vehicle, there has been spread a throttle grip apparatus structured such that it detects the rotation angle of a throttle grip using a throttle opening angle sensor and sends the thus-detected value as an electric signal to an electronic control device or a similar device carried on board the two-wheeled vehicle. The present throttle grip apparatus is also structured such that the electronic control device executes a given operation in accordance with the electric signal representing the detect value and, in accordance with the result of this operation, the ignition time of the engine of the vehicle or the opening and closing of an exhaust valve can be controlled (a throttle grip apparatus including such throttle opening angle sensor is disclosed, for example, in JP-A-4-254278).
Provision of the above-mentioned throttle opening angle sensor can eliminate the use of an operation cable which has been generally used to transmit the rotation operation of the throttle grip to the engine side. Also, the throttle angle sensor is stored in a case disposed at a position adjacent to the throttle grip; and, in the case, there is also stored a return spring composed of, for example, a torsion spring in order to energize the throttle grip into its initial state all the time. The above-mentioned throttle grip and composing elements to be operated in linking with the throttle grip are collectively referred to as a throttle grip apparatus.
In the above-mentioned conventional throttle grip apparatus, since the rotation angle of the throttle grip is detected using the throttle opening angle sensor, there is eliminated the need for provision of the operation cable which has been generally used for transmission of the rotation operation of the throttle grip to the engine side. However, no use of the operation cable causes the following problems.
That is, in the throttle grip apparatus including the operation cable, in case where the throttle grip is rotated, an inner tube is slided with respect to an outer tube which constitutes the operation cable, so that the sliding resistance of the inner tube is transmitted to the driver side. On the other hand, in the throttle grip apparatus including the throttle opening angle sensor, the power to be transmitted to the driver side when the throttle grip is rotated is limited only to the power that is generated by the return spring to return the throttle grip to the initial position, which strikes the driver as incongruous.
Also, in the throttle grip apparatus including the operation cable, the sliding friction to be generated when the throttle grip is rotated is different from that generated when the throttle grip is returned, thereby generating a so called hysteresis. On the other hand, the return spring composed of a torsion spring and the like is not able to generate such hysteresis and thus cannot eliminate the incongruous feel to be transmitted to the driver when the throttle grip is rotated.